Vehicle restraint systems that include an air bag mounted forward of the occupant's seating position are well known in the art. Such forward mounted restraint systems also include either an inertia switch or an accelerometer for sensing the occurrence of a crash condition. When a crash condition of sufficient severity is sensed, the associated forward mounted air bag is deployed.
Side mounted air bag restraint systems including an air bag mounted in the occupant's door are also known in the art. Prior art side mounted air bag restraint systems have included contact switches in the door. A crash into the door of sufficient severity results in actuation of the switch which, in turn, results in actuation of the door mounted air bag.
Some door mounted air bag restraint systems use an accelerometer for sensing a side crash. A controller is connected to the accelerometer. When the controller determines a side crash of sufficient severity is occurring, the associated side air bag is actuated. One example of such a system is disclosed in U.S. Pat. No. 5,202,831 to Blackburn et al.
A particular problem arises when the crash sensing accelerometer is mounted in the door having a door mounted air bag restraint system. This problem relates to the potential for inadvertent deployment of the door mounted air bag when the door is opened into a stationary object. When the opening door strikes the object, the sudden stopping of the door is "seen" by the accelerometer as being the same as a large impact into the door by an external object, i.e., in the same direction as would occur if another vehicle crashed into the door. This sudden stopping of the door could result in an output from the accelerometer that is misinterpreted by the associated controller as being a deployment crash condition and that results in deployment of the air bag by the controller.